Convert a column into a list - python-2.7

Question

I need to apply a for loop on a file containing records of a command, to convert one of the column into a list. Please advise, Thanks in advance .
Data is as below :
TOPIC PARTITION CURRENT-OFFSET LOG-END-OFFSET LAG
asset 8 100 1009663 1
asset 7 200 523533 1
asset 9 319710 319710 0
asset 5 870935 870935 0
This is my code :
lag_list = []
with open(fname) as f:
f.readline()
lines = f.readlines()[1: ]
length = len(lines)
print(length)
for line in lines:
print "Hello"
print line
print "hello 2"
data=line.split(' ')
lag_list.append(data[4])
data=line.split("\t")
lag_list.append(data[4])
print lag_list
return
But returning this error:
lag_list.append(data[4])
IndexError: list index out of range

Answer 1

Your data has
- not 4 tabs in a line
- or not 4 spaces in a line
- or you have a \n after the last line of your source data
When reading those lines and splitting them, you do not have 5 elements in the resulting list - hence index error when accessing data[4].
Splitting the same list by spaces and by tabs does not make much sense for me - I hope it does for your data and application.
Check your splitted list before indexing into it:
lag_list = []
with open(fname) as f:
f.readline()
lines = f.readlines()[1: ]
length = len(lines)
print(length)
for line in lines:
print "Hello"
print line
print "hello 2"
data = line.split(' ')
if len(data) >= 5: # check if safe to index into
lag_list.append(data[4]
else:
print("Not enough elements - need 5 at least:", data)
data = line.split("\t")
if len(data) >= 5: # check if safe to index into
lag_list.append(data[4])
else:
print("Not enough elements - need 5 at least:", data)
print lag_list
return